Mineral nutrient deficiencies constitute major limitations for plant growth on agricultural soils around the world. To identify genes that possibly play roles in plant K(+) nutrition, we employed the comparative proteome analysis for proteins isolated from Arabidopsis seedlings treated with K(+) deficiency for 3 h and 7 d. We identified genes including those encoding putative transcription factors, protein kinases, and phosphatases, proteins involved in phytohormone biosynthesis or signaling, proteins involved in carbon and energy metabolism, and other proteins possibly involved in signal transduction pathway such as 14-3-3 proteins and small G-protein. Our results suggest that those proteins may play roles in signal transduction pathways linking changes in extracellular K(+) status to alterations in gene expression facilitating K(+) homeostasis. These results yield a comprehensive picture of the post-transcriptional response for deprivation of K(+) and serve as a basic platform for further characterization of gene function and regulation in plant mineral nutrition.